D25-07 Feasibility Study Evaluating Acute Dysfunction in Posture and Balance Post Critical Illness: Pilot Physiological Data

Rationale Following an Intensive Care Unit (ICU) stay, patients experience fatigue and balance disturbance despite improvement in muscle weakness. No studies have investigated the physiology of postural control in this population despite known deficits in balance. We hypothesised that alterations in posture control contribute to symptoms experienced post critical illness. We collected pilot data of postural muscle activity during a feasibility study. Primary feasibility outcomes have previously been presented. Methods We recruited ICU survivors, who had been mechanically ventilated and had stayed on ICU for ≥4 days, 2-3 months after ICU discharge. Patients were excluded if their co-morbidities impacted balance. We collected electromyographic (EMG) data from postural muscles at several angles of incline using a tilt table. EMG onset of postural muscle activity during balance perturbation, induced by rapid upper limb movement, was measured. We compared postural muscle onset in our patients to that collected previously from a cohort of healthy participants. Additionally, we assessed the relationship between postural muscle onsets and physical/functional outcomes and measures of critical illness severity. Results 25 patients were recruited, 68% were male with a mean age of 57yrs (standard deviation 14yrs) and a median SOFA score of 12 (Inter-quartile range (IQR)10-14). Patients were recruited a median of 117 days (IQR: 105-135 days) after ICU discharge. At 90 degrees of tilt (i.e. vertical), onsets of the postural muscles erector spinae (ES) and external oblique (EO) were slower in ICU survivors than in healthy participants (ES ICU 54ms (IQR: 40-98ms) vs healthy -12ms (IQR: -26 to -6ms), p < 0.0001; EO ICU 47ms (IQR 30-76ms) vs healthy 0ms (IQR -3 to 2ms), p < 0.0001). In comparison to healthy participants, where onsets occurred at, or prior to the balance perturbation, onsets of activity in ICU patients occurred after the balance perturbation. Patients with worse balance (Berg Balance Scale (median 55, IQR 51-55) had a greater delayed onset of activity of ES (Spearman’s rho=-0.50, p = 0.01) and EO (rho=-0.40, p = 0.03). Similarly, patients with worse critical illness severity (measured by baseline SOFA score at ICU admission) had greater delays in postural muscle onset (ES Spearman’s rho=0.40, p = 0.08; EO, rho=0.46, p = 0.02). Conclusions These pilot data support changes in neurophysiological control of postural muscles in ICU survivors, suggesting an association of these changes with balance and severity of critical illness. A larger study is required to confirm these findings and further understand their implications. This could change the way rehabilitation is provided post critical illness.